Phased array systems and antennas for use in such systems are well known in, for example, telecommunications and radar applications. Such systems generally employ fixed, planar arrays of individual transmit and receive elements. When receiving electromagnetic (EM) signals, such as a communication signal or the return signal in a radar system, phased array systems receive signals at the individual elements and coherently reassemble the signals over the entire array by compensating for the relative phases and time delays between the elements. When transmitting signals, beams are electronically steered by delaying the excitation of selected individual radiating elements. For relatively small antennas, adequate delays of the individual elements can be provided by adjusting the phase of the excitation signals supplied to the elements.
Traditional phased-array antenna systems used in such applications were expensive to manufacture, were relatively large and bulky, and the performance was less than desirable due to, for example, relatively poor performance of monolithic microwave integrated circuits (MMICs) of the transceiver section of the antenna system. For example, such MMICs typically resulted in significant undesirable sidelobes which limited the usefulness of antennas using such circuits. Recent attempts at such antenna systems have included printing antenna system elements, such as signal traces and patch antennas, on a circuit board using well-known lithography techniques. Such antenna systems solve one problem in that they are smaller and relatively inexpensive to manufacture and, therefore, have been used increasingly in new applications. One such application is in adaptive cruise control systems in trucks, automobiles and other such vehicles. Such cruise control systems are able to reduce or increase the speed of the vehicle in order to maintain a predetermined distance between the vehicle and other traffic. Radar systems in vehicles are potentially also useful in such applications as collision avoidance and warning.